It must be Diocese to Diocese.
Cause I can’t find a thing on it.
I tried “Geographic location parish Catholic”
“Geographic restrictions parish Catholic”
“geographic restrictions parish requirement Catholic”
“How To Find a Good Catholic Parish”
With all these searches, I can’t find anything about requirements. They are required to take you but you can go anywhere. The only problem I could see is if in the 50’s, parishes got too big to handle everyone. Our St. Lawrence begat St. Matthias in 1965, because the congregation got too big. Some were told to go to St. Matthias.
But that wouldn’t happen today.